Process for the direct manufacture of iron and steel



P. BASSET. PROCESS FOR THE DIRECT MANUFACTURE OF IRON AND STEEL.

APPLICATION FILED FEB. 26, 1921.

Patented Nov. M, 1922.

Patented Nov. 14, 1922.

UNHTEED STATES LUCIEN PAUL BASSET, OF PARIS, FRANCE.

PROCESS FOR THE DIRECT MANUFACTURE OF IRON AND STEEL.

Application filed February 26, 1921. Serial No. 448,072.

T 0 all whom it may concern:

Be it known that I, LUCIEN PAUL BAssnr, of Paris, France, have inventeda certain new and useful Process for the Direct Manufacture of Iron andSteel (for which I have filed applications in France Feb. 24, 1920;Belgium May 1, 1920 and Luxemburg April 28, 1920), of which thefollowing is a specification.

In the manufacture of cast-iron in the blast furnace by the ordinarywell known processes, it is not possible to obtain a product free fromforeign metals and impurities.

Various foreign bodies are present. capable of being absorbed by themetal. These bodies have different properties relatively to the burden,and it is possible, by giving to the slag a predetermined composition,to prevent the absorption by the metal of one body or of a group ofbodies having some one or more common reactions. But such regulation ofthe slag has no effect on the action of other impurities or groups ofimpurities present. Hence in the manufacture of cast-iron, many of theimpurities can be gotten rid of, only by removal from the iron, by asubsequent operation, (refining operation).

Thus, it is not possible, by the usual metallurgical processesheretofore known, to directly obtain a metal both desulfurized anddephosphorized, as, in these processes, the desulfurization anddephosphorization are two rather dissimilar operations, requiringdifferent conditions; the first being a deoxidizing, (reducing)operation and the second an oxidizing operation.

Generally, a metalis required from the blast-furnace practically freefrom phosphorus. For that purpose, by the addition to the ore ofcalcareous fluxes, a basic line sla is produced which combines with thesulfur to form calcium sulfid. This calcareous slag being diflicultlyfusible, it is necessary, for causing it to melt, to operate at a hightemperature, but, at this high temperature, the coal mixed with the ore,acting as the heating agent as well as the reduction agent, stronglyreacts with all of the elements of the burden, which, apart from limeand alumina, are thus partially or entirely reduced; it therefore,follows that the metal produced, contains as impurities, silicon,manganese, phosphorus, etc. At this very high temperature, the slag isnearly completely free from oxide of iron; in fact, the latter, which isthe most easily reducible of the oxides present, is the first to bereduced to metal, and hence eliminated from the slag.

For preventing the reduction of silica, manganese compounds andphosphate of lime, it would be necessary to operate at a lowertemperature and conse uently, to provide a more easily fusible s ag,containing oxide of iron, but such a slag would be more highlysiliceous-than that above referred to, and accordingly, would not haveso good desulfurizin properties.

It will, tierefore, be seen that the desulfurizing and dephosphorizingoperations cannot be carried out together in the blast furnace, owing tothe fact that the coal acts at the same time as fuel and as reducingagent, and it is not possible to separate these two unctions.

My present invention has for its object a process of directly producingiron and steel, which will produce these metals in a form in which theycan be directly used, that is to say, practically free from sulfur andphosphorus.

This process consists, substantially:

(a) In heating in a furnace a mixture of ore and iron, coal and basicfluxes, if necessary, by means of a flame produced by the combustion ofeither coal pulverized to the condition of flour (i. e; in the form ofan impalpable powder) or of a finely pulverized hydrocarbon, such fuelbeing burned in preheated air in carefully regulated proportions,whereby this combustion gives practically only carbon monoxide;

(b) In regulating the reducing conditions in the furnace, so that thebasic calcareous slag may contain a small quantity of oxide of iron,proportional to the quantity of phosphorus contained in the ore andinversely proportional to the calcic-basicity of the slag.

In this process, the small quantity of oxide of iron left in the basicslag, checks the phosphoration of the metal, the reduction of silica andof manganese oxide, while maintaining the desulfurizing function of thecalcareous slag.

Besides, the heating and reducing operations. contrarily to what takesplace with the ordinary processes in the blast furnace, are keptdistinct from. each other, and it is easy to modify the working of oneof these operations without modifying the other.

By means of the present process, the sulfur and phosphorus, (present asimpurities in the ore), are fixed and taken up by the slag before theycan be absorbed by the metal, and as this fixation of the sulfur andphosphorus is produced at the same time as the production of the freemetal, the production of the latter in a pure state, is not delayed by asubsequent refining operation, such operation being unnecessary.

In order that the invention may be clearly understood, I will describe,by way of example, a method for carrying out the present process in arotary furnace constituted as diagrammatically illustrated in theaccompanying drawino which shows the furnace in longitudinaf sectionalview in two separated sections.

As shown in the drawing, this furnace comprises an inclined rotarycylindrical furnace a of great length, (for instance, a length of 50meters and a diameter of 2.5 meters). This cylinder has an internalrefractory lining and external rings 1) running on rollers. A toothedgear a? imparts a rotary motion to the furnace a.

At the lower end of the furnace a is proi vided an orifice 6 throughwhich enters a nozzle f; through the latter are injected hot air andpulverized coal in the form of an impalpable powder; the coal comingfrom a hopper g is re ularly discharged by a feed screw 72, of regu atedspeed, so that the supply of coal may be carefully regulated to give-thenecessary proportion for causing the combustion of this coal in thecylindrical body a to !produce practically only carbon monoxide. I

The air injected by the nozzle f is previously heated in a heatexchanger operated bya portion of the combustible gases issuingfrom thefurnace. The furnace at is provided, at its lower 7 end with tap holes71, j, the tap holes 71 being nozzle f.

arranged near the periphery of the furnace a, and the tap holes 7'nearer the axis ofthe latter. The tap holes 71, for the metal, are

normally closedbut are opened periodically;

the tap holes 7', for-the slag, remain always open.

If it is desired to continuously tap small quantities, one of thel-tapholes a will be left permanently open;-both metal and slag being tappedat each revolution, when this tap hole is at low points of itsrevolution.

At its other end, the furnace a opens into abrick-Work chamber k forreceiving the combustible a fan Zto points of use, a part being burnedfor heating the ,air to be injected by the The iron ore to be treated,mixed with fluxes and with the quantity of coal just short of theproportion sufficient for the complete reduction of thisore, is fed inat ases. These gases are sent by attains cherry red the coal continuesto burn alone. When the lower end of the furnace a is at white heat, theoperator ascertains if the proportions of air and coal are suitable forgiving only carbon monoxide, If this is not the case, these proportionsare adjusted ,to give this condition. Then, by means of the screw m theiron ore is introduced into the furnace; the iron ore is preferablyfinely crushed and is mixed with suitable fluxes for obtaining acalcareous slag and with the quantity of coal necessary for effectingthe reduction of about 95% of the iron oxid in ore. I

As previously stated, the quantity of iron oxid which is to be left inthe slag, will be proportional to the content of phosphorus in the oreand reversely proportional to the lime in the slag. Generally, anordinary basic calcareous slag containing 5% of iron oxid is amplysufficient for dephosphorizing the ores.

Under the effect of the inclination and rotation of the furnace, themixture regularly advances towards the hearth and is heated, the ironoxid is reduced in the proportion of 95% and the slag is formed, takingaway with it the 5% of iron oxid which have not been reduced, the metalmelts in theghottestzone and the metal and slag are tapped as abovedescribed.

In the present process, the only object of the flame is to heat, Thisflame gives essentially a mixture of nitrogen. carbon monoxid and of thehydrogen contained in the coal, and hence cannot exert any oxidizingaction on the metal produced and it exercisesonly a small part of thereduction of the iron ore.

The reduction is therefore eflected substantially entirely by the coal\mixed with the ore. It is therefore possible, by modifying theproportion of this coal, to vary the percentage of the iron oxid, whichwill be reduced. and hence the non-reduced fraction which goes into theslag.

This slag, containing a small and readily controllable proportion of'iron oxid, prevents by its oxidizing function, the phosphoration of themetal, the reduction of silica and oxide of manganese and, by its basicfunction, the sulfuration of .the metal.

Moreover, in the present process, the tendency to sulfuration is muchless in the blast duced to the metallic state, then a small quantity ofmetallic iron is re-oxidized, so asj to provide in the slag the requiredsmall quantity of iron oxid. For that purpose a "small excess of air issupplied to the hearth relatively to the coal projected by the nozzle,the flame produced by the combustion of this coal, will then contain asmall proportion of carbon dioxid and water vapor; both of which arepowerful oxidizing agents for iron at the temperature of the furnace,and they will accordingly reoxidize a small portion of the metallic ironproduced.

It is thus possible, by a judicious regulation of this additional air,to limit the reducing action of the coal mixed with the ore and to leavethe desired quantity of iron .oxid in the slag.

carried into practice-in other types of fur- The use of a rotary furnacehas been in dicated above 'as a preferred means for carrying out thepresent process, but it is to be understood that the latter can benaces.

'The' process forming the subject-matter of this invention permits thedirect production of iron andste'el. If it is desired to obtain carbondioxid and water vapor, in the continued presence'of a basic slagcontaining a small amount of iron oxid, whereby said slag preventsreduction of phosphorus, silicon and manganese compounds and the passageofthese elements into iron, and

also prevents the passage of sulfur into the metal.

2. A rocess of producing refined iron and steel direct which comprisesheating a mixture containing iron ore, lime, and a solid carbonaceousreducing agent,, by means of a flame free from: substantial amounts ofcarbon dioxid and water vapor, in the continued presence of a basic slagcontaining a small amount of iron oxid, whereby said slag preventsreduction of phosphorus, silicon and manganese compounds and the passageof these elements into iron, and also prevents the passage of sulfurinto the metal.

3. A process of producing refined iron and steel direct which comprisesheating a mixture containing iron ore, lime, and a solid carbonaceousreducing agent, by means of a flame free from substantial amounts ofcarbon dioxid and water vapor, agitatin and progressing the chargetoward said flame, durin such heating operation, in the continuepresence of a basic. slag containing a small amount of iron oxid, where--by said slag prevents reduction of phosphorus, silicon and manganesecompounds and the passage of these elements into iron, and also reventsthe passage of sulfur into themetall 4. In the process of claim 1, theimproveby the combustion of finely comminuted.

solid carbonaceous fuel, in a blast of preheated air, the relativeproportions of these being so adjusted as to roduce substantially onlycarbon mbnoxi to the substantial exclusion ofcarbon dioxid and watervapor.

5. In the process of claim 1, :mixing the iron ore with coal as thereducing agent.

6. In the process of claim 1, the step of mixing the iron ore with anamount of coal which is slightly less than that amount which would benecessary to reduce all of the iron oxid to metal.

7. In the process of claim 1, the ment which comprises conducting theoperations in an inclined rotary furnace, the ore being'fed at the upperend and the flame being sup lied at the lower end.

"The oregoing specification of Pro- I cess for the direct manufactureand refining of iron and steel, signed by me this 9th day of February1921.

LUCIEN PAUL'BASSET.

improve-

